System for providing a continuous motion sequential lateral solidification

ABSTRACT

A method and system for processing an amorphous silicon thin film sample to produce a large grained, grain boundary-controlled silicon thin film. The film sample includes a first edge and a second edge. In particular, using this method and system, an excimer laser is used to provide a pulsed laser beam, and the pulse laser beam is masked to generate patterned beamlets, each of the patterned beamlets having an intensity which is sufficient to melt the film sample. The film sample is continuously scanned at a first constant predetermined speed along a first path between the first edge and the second edge with the patterned beamlets. In addition, the film sample is continuously scanned at a second constant predetermined speed along a second path between the first edge and the second edge with the patterned beamlets.

CROSS-REFERENCE TO A RELATED A

This application is a divisional application U.S. patent applicationSer. No. 09/526,585, filed on Mar. 16, 2000, now U.S. Pat. No.6,368,945.

NOTICE OF GOVERNMENT RIGHTS

The U.S. Government has certain rights in this invention pursuant to theterms of the Defense Advanced Research Project Agency award numberN66001-98-1-8913.

FIELD OF THE INVENTION

The present invention relates to a method and system for processing athin-film semiconductor material, and more particularly to forminglarge-grained grain boundary-location controlled semiconductor thinfilms from amorphous or polycrystalline thin films on a substrate usinglaser irradiation and a continuous motion of the substrate having thesemiconductor film being irradiated.

BACKGROUND INFORMATION

In the field of semiconductor processing, there have been severalattempts to use lasers to convert thin amorphous silicon films intopolycrystalline films. For example, in James Im et al., “Crystalline SiFilms for Integrated Active-Matrix Liquid-Crystal Displays,” 11 MRSBulletin 39 (1996), an overview of conventional excimer laser annealingtechnology is described. In such conventional system, an excimer laserbeam is shaped into a long beam which is typically up to 30 cm long and500 micrometers or greater in width. The shaped beam is stepped over asample of amorphous silicon to facilitate melting thereof and theformation of grain boundary-controlled polycrystalline silicon upon theresolidification of the sample.

The use of conventional excimer laser annealing technology to generatepolycrystalline silicon is problematic for several reasons. First, thepolycrystalline silicon generated in the process is typically smallgrained, of a random micro structure (i.e., poor control of grainboundaries), and having a nonuniform grain sizes, therefore resulting inpoor and nonuniform devices and accordingly, low manufacturing yield.Second, in order to obtain acceptable quality grain boundary-controlledpolycrystalline thin films, the manufacturing throughput for producingsuch thin films must be kept low. Also, the process generally requires acontrolled atmosphere and preheating of the amorphous silicon sample,which leads to a reduction in throughput rates. Accordingly, thereexists a need in the field to generate higher quality thinpolycrystalline silicon films at greater throughput rates. Therelikewise exists a need for manufacturing techniques which generatelarger and more uniformly microstructured polycrystalline silicon thinfilms to be used in the fabrication of higher quality devices, such asthin film transistor arrays for liquid crystal panel displays.

SUMMARY OF THE INVENTION

An object of the present invention is to provide techniques forproducing large-grained and grain boundary location controlledpolycrystalline thin film semiconductors using a sequential lateralsolidification process and to generate such silicon thin films in anaccelerated manner.

At least some of these objects are accomplished with a method and systemfor processing an amorphous or polycrystalline silicon thin film sampleinto a grain boundary-controlled polycrystalline thin film or a singlecrystal thin film. The film sample includes a first edge and a secondedge. In particular, using this method and system, a laser beamgenerator is controlled to emit a laser beam, and portions of this laserbeam are masked to generate patterned beamlets, each of the beamletshaving an intensity which is sufficient to melt the film sample. Thefilm sample is continuously scanned at a first constant predeterminedspeed along a first path between the first edge and the second edge bythe patterned beamlets. In addition, the film sample is continuouslyscanned at a second constant predetermined speed along a second pathbetween the first edge and the second edge by the patterned beamlets.

In another embodiment of the present invention, the film sample iscontinuously translated in a first direction so that the fixed patternedbeamlets continuously irradiate successive first portions of the filmsample along the first path. The first portions are melted while beingirradiated. In addition, the film sample is continuously translated in asecond direction so that the fixed patterned beamlets irradiatesuccessive second portions of the film sample along the second path. Thesecond portions are melted while being irradiated. Furthermore, afterthe film sample is translated in the first direction to irradiate a nextsuccessive portion of the first path of the film sample, the firstportions are cooled and resolidified, and after the film sample istranslated in the second direction to irradiate a next successiveportion of the second path of the film sample, the second portions arecooled and resolidified.

In yet another embodiment of the present invention, the film sample ispositioned so that the patterned beamlets impinge at a first locationoutside of boundaries of the film sample with respect to the filmsample. Also, the film sample can be microtranslated from the firstlocation to a second location before the film sample is scanned alongthe second path, starting from the second location.

In a further embodiment of the present invention, after the film sampleis scanned along the second path, the film sample is translated so thatthe beamlets impinge a third location which is outside the boundaries ofthe film sample microtranslated. Thereafter, the film sample can bestepped so that the impingement of the beamlets moves from the thirdlocation to a fourth location, the fourth location being outside of theboundaries of the film sample. Then, the film sample is maintained withthe patterned beamlets impinging on the fourth location until the filmsample stops vibrating and after the movement of the film sample ceases.

In another embodiment of the present invention, the film sample iscontinuously scanned in a first direction so that the fixed positionbeamlets scan the first path, and then in a second direction so that thefixed position beamlets scan the second path. After the film sample istranslated in the first direction, it is continuously translated at thefirst constant predetermined speed in a second direction so that thepatterned beamlets irradiate the first successive portions of the filmsample along the second path, the second direction being opposite to thefirst direction. Then, the film sample is microtranslated so that theimpingement of the beamlets moves from the first location to a secondlocation, the second location being outside of boundaries of the filmsample. Thereafter, the film sample is continuously translated at thesecond constant predetermined speed in a first direction so that thepatterned beamlets irradiate second successive portions of the filmsample along the second path until the beamlets impinge on the secondlocation, the first direction being opposite to the second direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a shows a diagram of an exemplary embodiment of a system forperforming a continuous motion solidification lateral solidification(“SLS”) according to the present invention.

FIG. 1b shows an embodiment of a method according of the presentinvention for providing the continuous motion SLS which may be utilizedby the system of FIG. 1a.

FIG. 2a shows a diagram of a mask having a dashed pattern.

FIG. 2b shows a diagram of a portion of a crystallized silicon filmresulting from the use of the mask shown in FIG. 2a in the system ofFIG. 1a.

FIG. 3a shows a diagram of a mask having a chevron pattern.

FIG. 3b shows a diagram of a portion of a crystallized silicon filmresulting from the use of the mask shown in FIG. 3a in the system ofFIG. 1a.

FIG. 4a shows a diagram of a mask having a line pattern.

FIG. 4b shows a diagram of a portion of a crystallized silicon filmresulting from the use of the mask shown in FIG. 4a in the system ofFIG. 1a.

FIG. 5a shows an illustrative diagram showing portions of irradiatedareas of a silicon sample using a mask having the line pattern.

FIG. 5b shows an illustrative diagram of the portions of the irradiatedareas of a silicon sample using a mask having a line pattern afterinitial irradiation and sample translation has occurred, and after asingle laser pulse during the method illustrated in FIG. 1b.

FIG. 5c shows an illustrative diagram of the portions of thecrystallized silicon film after a second irradiation has occurred whichwas generated using the method illustrated in FIG. 1b.

FIG. 6a shows a mask having a diagonal line pattern.

FIG. 6b a diagram of a portion of a crystallized silicon film resultingfrom the use of the mask shown in FIG. 6a in the system of FIG. 1a;

FIG. 7 shows another embodiment of a method according of the presentinvention for providing the continuous motion SLS which may be utilizedby the system of FIG. 1a.

FIG. 8 shows a flow diagram illustrating the steps implemented by themethod illustrated in FIG. 1b.

DETAILED DESCRIPTION

The present invention provides techniques for producing uniformlarge-grained and grain boundary location controlled crystalline thinfilm semiconductors using the sequential lateral solidification process.In order to fully understand those techniques, the sequential lateralsolidification process must first be appreciated.

The sequential lateral solidification process is a technique forproducing large grained silicon structures through small-scaleunidirectional translation of a sample in having a silicon film betweensequential pulses emitted by an excimer laser. As each pulse is absorbedby the silicon film, a small area of the film is caused to meltcompletely and resolidify laterally into a crystal region produced bythe preceding pulses of a pulse set.

An advantageous sequential lateral solidification process and anapparatus to carry out that process are disclosed in co-pending patentapplication Ser. No.09/390,537 (the “'537 application”) filed on Sep. 3,1999, and assigned to the common assignee, the entire disclosure ofwhich is incorporated herein by reference. While the foregoingdisclosure is made with reference to the particular techniques describedin the '537 application, it should be understood that other sequentiallateral solidification techniques could easily be adapted for the use inthe present invention.

FIG. 1a shows a system according to the present invention which iscapable of implementing the continuous motion SLS process. As alsodescribed in the '537 application, the system includes an excimer laser110, an energy density modulator 120 to rapidly change the energydensity of a laser beam 111, a beam attenuator and shutter 130 (which isoptional in this system), optics 140, 141, 142 and 143, a beamhomogenizer 144, a lens and beam steering system 145, 148, a maskingsystem 150, another lens and beam steering system 161, 162, 163, anincident laser pulse 164, a thin silicon film sample on a substrate 170,a sample translation stage 180, a granite block 190, a support system191, 192, 193, 194, and a computer 100 which manages X and Y directiontranslations and microtranslations of the silicon film sample andsubstrate 170. The computer 100 directs such translations and/ormicrotranslations by either a movement of a mask within masking system150 or by a movement of the sample translation stage 180.

As described in further detail in the '537 application, an amorphoussilicon thin film sample is processed into a single or polycrystallinesilicon thin film by generating a plurality of excimer laser pulses of apredetermined fluence, controllably modulating the fluence of theexcimer laser pulses, homogenizing the modulated laser pulses in apredetermined plane, masking portions of the homogenized modulated laserpulses into patterned beamlets, irradiating an amorphous silicon thinfilm sample with the patterned beamlets to effect melting of portionsthereof irradiated by the beamlets, and controllably translating thesample with respect to the patterned beamlets and with respect to thecontrolled modulation to thereby process the amorphous silicon thin filmsample into a single or grain boundary-controlled polycrystallinesilicon thin film by the sequential translation of the sample relativeto the patterned beamlets and irradiation of the sample by patternedbeamlets of varying fluence at corresponding sequential locationsthereon. The following embodiments of the present invention will now bedescribed with reference to the foregoing processing technique.

FIG. 1b shows an embodiment of a process according of the presentinvention for providing the continuous motion SLS which may utilize thesystem described above. In particular, the computer 100 controls themotion (in the planar X-Y direction) of the sample translation stage 180and/or the movement of the masking system 150. In this manner, thecomputer 100 controls the relative position of the sample 170 withrespect to the pulsed laser beam 149 and the final pulsed laser beam164. The frequency and the energy density of the final pulsed laser beam164 are also controlled by the computer 100.

As described in co-pending patent application Ser. No. 09/390,535 (the“'535 application”) filed on Sep. 3, 1999, and also assigned to thecommon assignee, the entire disclosure of which is incorporated hereinby reference, the sample 170 may be translated with respect to the laserbeam 149, either by moving the masking system 150 or the sampletranslation stage 180, in order to grow crystal regions in the sample170. For example, for the purposes of the foregoing, the length andwidth of the laser beam 149 may be 2 cm in the X-direction by ½ cm inthe Y-direction (e.g., a rectangular shape), but the pulsed laser beam149 is not limited to such shape and size. Indeed, other shapes and/orsizes of the laser beam 149 are, of course, achievable as is known tothose having ordinary skill in the art (e.g., square, triangle, etc.).

Various masks may also be utilized to create the final pulsed laser beamand beamlets 164 from the transmitted pulsed laser beam 149. Someexamples of the masks are shown in FIGS. 2a, 3 a, 4 a and 6 a, adetailed description of which has already been provided in the '535application. For example, FIG. 2a shows a mask 210 incorporating aregular pattern of slits 220, FIG. 3a shows a mask 310 incorporating apattern of chevrons 320, and FIG. 6a shows a mask 610 incorporating apattern of diagonal lines 620. For the sake of simplicity, providedbelow is a description of the process accordingly to the presentinvention which utilizes a mask 410 (shown in FIG. 4a) incorporating apattern of slits 410, each of which may extend as far across on the mask410 as the homogenized laser beam 149 incident on the mask 410 permits,and should have a width 440 that is sufficiently narrow to prevent anynucleation from taking place in the irradiated region of the sample 170.As discussed in the '535 application, the width 440 may depend on anumber of factors, e.g., the energy density of the incident laser pulse,the duration of the incident laser pulse, the thickness of the siliconthin film sample, the temperature and thermal conductivity of thesilicon substrate, etc.

In the exemplary embodiment shown in FIG. 1b, the sample 170 has thesize of 40 cm in the Y-direction by 30 cm in the X-direction. The sample170 is conceptually subdivided into a number of columns (e.g., a firstcolumn 5, a second column 6, etc.), and the location/dimension of eachcolumn is stored in a storage device of the computer 100, and utilizedby the computer 100. Each of the columns is dimensioned, e.g., 2 cm inthe X-direction by 40 cm in the Y-direction. Thus, the sample 170 may beconceptually subdivided into, e.g., fifteen columns. It is alsoconceivable to conceptually subdivide the sample 170 into columns havingdifferent dimensions (e.g., 3 cm by 40 cm columns, etc.). When thesample 170 is conceptually subdivided into columns, at least a smallportion of one column extending for the entire length of such columnshould be overlapped by a portion of the neighboring column to avoid apossibility of having any unirradiated areas. For example, theoverlapped area may have a width of, e.g.,1 μm.

After the sample 170 is conceptually subdivided, a pulsed laser beam 111is activated (by actuating the excimer laser using the computer 100 orby opening the shutter 130) and produces the pulsed laser beamlets 164impinging on a first location 20 (from the pulsed laser beam 149). Then,the sample 170 is translated and accelerated in the forward Y-directionunder the control of the computer 100 to reach a predetermined velocitywith respect to the fixed position beamlets in a first beam path 25.Using the equation:

Vmax=Bw·f,

where Vmax is a maximum possible velocity that the sample 170 can bemoved with respect to the pulsed beamlets 164, Bw is the width of thepattern of the pulsed laser beamlets 164 (or the width of the envelopeof the pulsed beamlets 164), and f is the frequency of the pulsedbeamlets 164, the predetermined velocity Vpred can be determined usingthe following:

Vpred=Vmax−K,

where K is a constant, and is utilized to avoid a possibility of havingany unirradiated areas between adjacent irradiated areas. It is alsopossible to use the system according to the present inventionillustrated in FIG. 1a without utilizing the beam attentuator andshutter 130, since (as described below) due to the continuoustranslation of the sample 170, the pulsed beamlets 164 does not have tobe blocked or turned off.

The pulsed beamlets 164 reach an upper edge 10′ of the sample 170 whenthe velocity of the movement of the sample 170 with respect to thepulsed laser beam 149 reaches the predetermined velocity Vpred. Then,the sample 170 is continuously (i.e., without stopping) translated inthe forward Y-direction at the predetermined velocity Vpred so that thepulsed beamlets 164 continue irradiating successive portions of thesample 170 for an entire length of a second beam path 30. When thepulsed beamlets 164 reach a lower edge 10″ of the sample 170, thetranslation of the sample 170 is slowed with respect to the pulsedbeamlets 164 (in a third beam path 35) to reach a second location 40.After the pulsed beamlets 164 continuously and sequentially irradiatedthe successive portions of the sample 170 along the second beam path 30,these successive portions of the sample 170 are fully melted. It shouldbe noted that after the pulsed beamlets 164 pass the lower edge 10″ ofthe sample 170, a crystalized silicon thin film area 540 (e.g., grainboundary-controlled polycrystalline silicon thin film) forms in theirradiated second beam path 30 area of the sample 170, a portion ofwhich is shown in FIG. 5b. This grain boundary-controlledpolycrystalline silicon thin film area 540 extends for the entire lengthof the second irradiated beam path 30. It should be noted that it is notnecessary to shut down the pulsed laser beam 149 after the pulsedbeamlets 164 have crossed the lower edge 10″ of the sample 170 becauseit is no longer irradiating the sample 170.

Thereafter, to eliminate the numerous small initial crystals 541 thatform at melt boundaries 530 and while the location along the Y-directionof the pulsed beamlets 164 is fixed, the sample 170 is microtranslatedfor a predetermined distance (e.g., 3 micrometers) in the X-directionalong a fourth beam path 45 to reach a third location 47, and is thenaccelerated in the reverse Y-direction (toward the top edge 10′ of thesample 170) under the control of the computer 100 to reach thepredetermined velocity of translation with respect to the pulsedbeamlets 164 along a fourth beam path 50. The pulsed beamlets 164 reachthe lower edge 10″ of the sample 170 when the velocity of the sample 170with respect to the pulsed beamlets 164 reaches the predeterminedvelocity Vpred. The sample 170 is continuously translated (i.e., withoutstopping) in the reverse Y-direction at the predetermined velocity Vpredso that the pulsed beamlets 164 irradiate the sample 170 for the entirelength of a fifth beam path 55. When the sample 170 is translated underthe control of the computer 100 so that the pulsed beamlets 164 reachthe upper edge 10′ of the sample 170, the continuous translation of thesample 170 is again slowed with respect to the pulsed beamlets 164 (in asixth beam path 60) to reach a fourth location 65. The result of suchirradiation of the fifth beam path 55 is that regions 551, 552, 553 ofthe sample 170 (shown in FIG. 5b) cause the remaining amorphous siliconthin film 542 and the initial crystallized regions 543 of thepolycrystalline silicon thin film area 540 to melt, while leaving thecentral section 545 of the polycrystalline silicon thin film to remainsolidified. After the pulsed beamlets 164 continuously and sequentiallyirradiated the successive portions of the sample 170 along the fifthbeam path 55, these successive portions of the sample 170 are fullymelted. Thus, as a result of the laser beam 149's continuous (i.e.,without a stoppage) irradiation of the first column 5 for its entirelength in the fifth beam path 55, the crystal structure which forms thecentral section 545 outwardly grows upon solidification of meltedregions 542, 542 of the thin film which were formed as a result of thecontinuous irradiation along the second beam path 30. Thus, adirectionally controlled long grained polycrystalline silicon thin filmis formed on the sample 170 along the entire length of the fifth beampath 55. A portion of such crystallized structure is illustrated in FIG.5c. Therefore, using the continuous motion SLS procedure describedabove, it is possible to continuously form the illustrated crystallizedstructure along the entire length of the column of the sample 170.

Then, the sample 170 is stepped to the next column 6 to reach a fifthlocation 72 via a seventh beam path 70, and the sample is allowed tosettle at that location to allow any vibrations of the sample 170 thatmay have occurred when the sample 170 was stepped to the fifth location72 to cease. Indeed, for the sample 170 to reach the second column 6, itis stepped approximately 2 cm for the columns having a width (in theX-direction) of 2 cm. The procedure described above with respect to theirradiation of the first column 5 may then be repeated for the secondcolumn 6. In this manner, all columns of the sample 170 can be properlyirradiated with only a minimal settling time which may be required forthe sample 170 to settle (and thus wait for the vibrations of the sample170 to stop). Indeed, the only time that may be required for settlingthe sample 170 is when the laser has completed the irradiation of anentire column (e.g., the first column 5) of the sample 170, and thesample 170 is stepped to the next column (e.g., the second column 6) ofthe sample 170. Using the exemplary dimensions of the sample 170described above (30 cm by 40 cm), since each column is dimensioned 2 cmby 40 cm, there are only 15 columns that must be irradiated for thisexemplary sample 170. Accordingly, the number of “step and settle”delays that may occur for the exemplary sample 170 is either 14 or 15.

To illustrate the time savings in using the continuous motion SLSprocedure according to the present invention for producing thecrystallized silicon thin film, it is possible that the time it takes totranslate the sample 170 (which has the sample, column and laser beamdimensions discussed above) for the entire lengths in the various travelpaths of the sample 170 is estimated below:

the first beam path 25 0.1 seconds, the second beam path 30 0.5 seconds(since the sample 170 does not have to stop and settle for the entirelength of a column, and translates continuously), the third beam path 350.1 seconds, the fourth beam path 45 0.1 seconds, the fifth beam path 500.1 seconds, the sixth beam path 55 0.5 seconds (again because thesample 170 does not have to stop and settle for the entire length of acolumn, and translates continu- ously), the seventh beam path 60 0.1seconds, and the eight beam path 70 0.1 seconds.

Thus, the total time that it takes to completely irradiate each column5,6 of the sample is 1.6 seconds (or at most, e.g., 2 seconds). Thus,for 15 columns of the sample 170, the total time that it takes to formthe grain boundary-controlled polycrystalline structure thin film (forthe entire sample 170) is approximately 30 seconds.

As indicated above, it is also possible to use different dimensionsand/or shapes for cross-sectional area of the laser beam 149. Forexample, it is possible to use the pulsed laser beam 149 which has thecross-sectional area dimensioned 1 cm by 1 cm (i.e., a square shape). Itshould be appreciated that it is advantageous to use the diameter of thepulsed beamlets 164 as one of the dimension parameters of the columns.In this instance, the 30 cm by 40 cm sample 170 may be conceptuallysubdivided into 30 columns, each column being dimensioned 1 cm in theX-direction by 40 cm in the Y-direction (assuming a cross-section of adiameter of the pattern of the pulsed beamlets 164 of 1 cm). Using sucha pattern of the pulsed beamlets 164, it may be possible to increase thepredetermined velocity Vpred for translating the sample 170, andpossibly decrease the total energy of the pulsed laser beam 149. In thismanner, instead of irradiating the sample via 15 columns, the system andmethod according to the present invention would irradiate the sample via30 columns. Even though it may take longer to step and settle fromcolumn to column for 30 columns (as opposed to 15 columns describedabove), the speed of the sample translation may be increased because,due to the column's smaller width, the intensity of the pulsed laserbeam 149 can be greater, as a result of concentrating the laser pulseenergy into a smaller beamlet pattern, to provide effectivecrystallization of the sample 170, and the total time to complete theirradiation of the sample 170 may not be significantly higher than thatfor the sample which has 15 columns.

According to the present invention, any mask described and shown in the'535 application may be used for the continuous motion SLS procedureillustrated in FIG. 1b. For example, when the mask 310 is used inmasking system 150, a processed sample (i.e., a portion 350 shown inFIG. 3b having crystallized regions 360) is produced. Each crystalregion 360 will consist of a diamond shaped single crystal region 370and two long grained, directionally controlled grain boundarypolycrystalline silicon regions 380 in the tails of each chevron. Onemay also use a mask 610 (shown in FIG. 6a) incorporating a pattern ofdiagonal slits 620. For this mask 610, when the sample 170 iscontinuously translated in the Y-direction, and the mask 610 is used inthe masking system 150 of FIG. 1 a, a processed sample (a portion 650shown in FIG. 6b having crystallized regions 660) is produced. Eachcrystallized region 660 will consist of long grained, crystallineregions with directionally-controlled grain boundaries 670.

It is also possible to irradiate the sample 170 along the columns whichare not parallel to the edges of the square sample 170. For example, thecolumns may extend at approximately 45 degree angle with respect to theedges of the sample 170. The computer 100 stores start and end points ofeach column and is capable of performing the procedure shown in FIG. 1balong parallel columns which are slanted at, e.g., 45 degrees withrespect to the edges of the sample 170. The sample 170 can also beirradiated along parallel columns which are slanted at other angles withrespect to the edges of the sample 170 (e.g., 60 degrees, 30 degrees,etc.).

In another exemplary embodiment of the method according to the presentinvention which is shown in FIG. 7, the sample 170 is conceptuallysubdivided into a number of columns. After the sample 170 is subdivided,the pulsed laser beam 149 can be turned on (by actuating the excimerlaser using the computer 100 or by opening the shutter 130) so that itproduces the pulsed beamlets 164 which initially impinge on the firstlocation 20 (similarly to the embodiment illustrated in FIG. 1b). Then,the sample 170 is translated and accelerated in the Y-direction underthe control of the computer 100 to reach the predetermined sampletranslation velocity Vpred with respect to the pulsed beamlets 164 in afirst beam path 700. The pulsed beamlets 164 (and the beamlets) reach anupper edge 10′ of the sample 170 when the velocity of the translation ofthe sample 170 with respect to the pulsed laser beam 149 reaches thepredetermined velocity Vpred. Then, the sample 170 is continuously(i.e., without stopping) translated in the Y-direction at thepredetermined velocity Vpred continuously and sequentially so that thepulsed beamlets 164 irradiate the sample 170 for an entire length of asecond beam path 705. When the pulsed beamlets 164 reach the lower edge10″ of the sample 170, the translation of the sample 170 is slowed withrespect to the pulsed beamlets 164 (in a third beam path 710) to reach asecond location 715. It should be noted that after the pulsed beamlets164 pass the lower edge 10″ of the sample 170, the entire portion of thesample 170 along the second beam path 705 has undergone sequential fullmelting and solidification.

The sample 170, without microtranslating in the X-direction, istranslated back in the opposite Y-direction toward the upper edge 10′ ofthe sample 170. In particular, the sample 170 is accelerated in thenegative Y-direction under the control of the computer 100 along afourth beam path 720 to reach the predetermined sample translationvelocity Vpred prior to reaching the lower edge 10″ of the sample 170.Then, the sample 170 is continuously (i.e., without stopping) translatedin the negative Y-direction at the predetermined velocity Vpred so thatthe pulsed beamlets 164 continuously and sequentially irradiate thesample 170 along the entire length of a fifth beam path 725 (along thepath of the second beam path 705). When the pulsed beamlets 164 reachthe upper edge 10′ of the sample 170, the translation of the sample 170is slowed with respect to the pulsed beamlets 164 (in a sixth beam path730) until the beamlets 164 impinge on the first location 20. It shouldbe noted that after the pulsed beamlets 164 pass the upper edge 10′ ofthe sample 170, the entire portion of the sample 170 which wasirradiated along the second beam path 705 has undergone sequentialmelting and solidification. Accordingly, when this pass is completed,the surface of the sample 170 corresponding to the fifth beam path 725is partially melted and resolidified. In this manner, the resulting filmsurface may be further smoothed out. In addition, using this technique,the energy output of the pulsed laser beam 149 (and of the pulsedbeamlets 164) may be decreased to effectively smooth out the surface ofthe film. Similarly to the technique of FIG. 1b, a grainboundary-controlled polycrystalline silicon thin film area 540 forms inthe irradiated regions of the sample 170, a portion of which is shown inFIG. 5b. This grain boundary-controlled polycrystalline silicon thinfilm area 540 extends for the entire length of the second and fifthirradiated beam paths 705, 725. Again, it is not necessary to shut downthe pulsed laser beam 149 after the pulsed beamlets 164 have crossed thelower edge 10″ of the sample 170, and is no longer irradiates the sample170.

Thereafter, the sample 170 is microtranslated for a predetermineddistance (e.g., 3 micrometers) in the X-direction along a seventh beampath 735 until the pulse beamlets impinge on a third location 740, andis then again accelerated in the forward Y-direction (toward the loweredge 10″ of the sample 170) under the control of the computer 100 toreach the predetermined velocity Vpred with respect to the pulsedbeamlets 164 along an eighth beam path 745. The pulsed beamlets 164reach an upper edge 10′ of the sample 170 when the velocity oftranslation of the sample 170 with respect to the pulsed beamlets 164reach the predetermined velocity Vpred. Then, the sample 170 iscontinuously (i.e., without stopping) translated in the forwardY-direction at the predetermined velocity Vpred so that the pulsedbeamlets 164 continuously and sequentially irradiate the sample 170 foran entire length of a ninth beam path 750. When the pulsed beamlets 164reach the lower edge 10″ of the sample 170, the translation of thesample 170 is slowed with respect to the pulsed beamlets 164 (in a tenthbeam path 760) until the pulsed beamlet 164 impinge on a fourth location765. It should be noted that after the final pulsed laser beam 164 passthe lower edge 10″ of the sample 170, the entire portion of the sample170 which was irradiated along the ninth beam path 750 has undergonesequential full melting and resolidification.

Thereafter, without microtranslating, the direction of the translationof the sample 170 is again reversed (via beam paths 770, 775, 780), andthese paths of the sample 170 are again each continuously andsequentially irradiated by continuously translating the sample 170 inthe reverse Y-direction (which also extends along the ninth beam path750) at the predetermined velocity Vpred. Accordingly, when this pass iscompleted, the surface of the sample 170 corresponding to the beam path775 is partially melted and resolidified. The surface of these paths745-780 is smoothed out as a result of the forward and reverseY-direction translation and irradiation along the same beam path of thesample 170 (without microtranslation). The final product of suchprocedure is the creation of large-grained, grain boundary-controlledcrystalized structure along the entire column (e.g., dimensioned 2 cm by40 cm) of the sample 170, having a flat (or flatter) surface.

Then, the sample 170 is stepped to the next column (i.e., the secondcolumn 6) until the beamlets impinge on a fifth location 790 via anotherbeam path 785, and the sample 170 is allowed to settle to damp out anyvibrations of the sample 170 and stage 180 that may have occurred whenthe sample 170 was stepped where the pulsed beamlets 164 impinge on thefifth location 790. The procedure is repeated for all columns of thesample 170, similarly to the procedure described above and illustratedin FIG. 1b.

Referring next to FIG. 8, the steps executed by computer 100 to controlthe thin silicon film crystallization growth method implementedaccording of the procedure shown in FIG. 1b and/or FIG. 7 is describedbelow. For example, various electronics of the system shown in FIG. 1aare initialized in step 1000 by the computer 100 to initiate theprocess. A thin amorphous silicon film sample on a substrate 170 is thenloaded onto the sample translation stage 180 in step 1005. It should benoted that such loading may be either manual or robotically implementedunder the control of the computer 100. Next, the sample translationstage 180 is moved into an initial position in step 1015, which mayinclude an alignment with respect to reference features on the sample170. The various optical components of the system are adjusted andfocused in step 1020, if necessary. The laser is then stabilized in step1025 to a desired energy level and pulse repetition rate, as needed tofully melt the amorphous silicon sample over the cross-sectional area ofeach pulsed beamlet incident on the sample in accordance with theparticular processing to be carried out. If necessary, the attenuationof the pulsed beamlets 164 is finely adjusted in step 1030.

Next, the shutter can be opened (or the computer activates to turn onthe pulsed laser beam 149) in step 1035 to irradiate the sample 170 bythe pulsed beamlets 164 and accordingly, to commence the continuousmotion sequential lateral solidification method illustrated in FIGS. 1band 7. The sample is translated in the Y-direction continuously while afirst beam path of the sample (e.g., the sample along the second beampath 30) is continuously and sequentially irradiated (step 1040). Thesample 170 is translated in the Y-direction continuously at thepredetermined velocity Vpred while a second beam path of the sample(e.g., the sample along the sixth beam path 55) is sequentially andcontinuously irradiated (step 1045). With respect to FIG. 1b, this canbe seen by the continuous translation of the sample 170 along the secondbeam path 30 while the sample 170 is being continuously and sequentiallyirradiated, then slowing down along the third beam path 35,microtranslating the sample along the X-direction along the fourth beampath 45, waiting for the sample 170 to settle, accelerating along thefifth beam path 50, and then continuously translating the sample 170along the sixth beam path 55 while the sample 170 is being continuouslyand sequentially irradiated. In this manner, an entire column of thesample 170 is sequentially irradiated. If some portion of the currentcolumn of the sample 170 is not irradiated, the computer 100 controlsthe sample 170 to continuously translate at the predetermined velocityVpred in a particular direction so that another portion of the currentcolumn of the sample 170 which has not yet been irradiated, isirradiated (step 1055).

Then, if the crystallization of an area of the sample 170 has beencompleted, the sample is repositioned with respect to the pulsedbeamlets 164 in steps 1065, 1066 (i.e., moved to the next column orrow—the second column 6) and the crystallization process is repeated onthe new path. If no further paths have been designated forcrystallization, the laser is shut off in step 1070, the hardware isshut down in step 1075, and the process is completed in step 1080. Ofcourse, if processing of additional samples is desired or if the presentinvention is utilized for batch processing, steps 1005, 1010, and1035-1065 can be repeated on each sample. It is well understood by thosehaving ordinary skill in the art that the sample may also becontinuously translated in the X-direction, and microtranslated in theY-direction. Indeed, it is possible to continuously translate the sample170 in any direction so long as the travel paths of the pulsed beamlets164 are parallel, continuous and extend from one edge of the sample 170to another edge of the sample 170.

The foregoing merely illustrates the principles of the presentinvention. Various modifications and alterations to the describedembodiments will be apparent to those skilled in the art in view of theteachings herein. For example, the thin amorphous or polycrystallinesilicon film sample 170 may be replaced by a sample having pre-patternedislands of such silicon film. In addition, while the exemplaryembodiments above have been described for laser systems in which thelaser beams are fixed and preferably not scannable, it should berecognized that the method and system according to the present inventioncan utilize a pulsed laser beam which can be deflected at a constantspeed along a path of a fixed sample. It will thus be appreciated thatthose skilled in the art will be able to devise numerous systems andmethods which, although not explicitly shown or described herein, embodythe principles of the present invention, and are thus within the spiritand scope of the present invention.

What is claimed is:
 1. A system for processing a polycrystalline siliconthin film sample into a crystalline thin film, the film sample having afirst edge and a second edge, the system comprising: a memory storing acomputer program; and a processing arrangement which, when executing thecomputer program, is configured to perform the following steps: (a)controlling a laser beam generator to emit a laser beam, (b) maskingportions of the laser beam to generate patterned beamlets, each of thepatterned beamlets impinging on the film sample having an intensitywhich is sufficient to melt the film sample, (c) continuously scanning,at a first constant predetermined speed, the film sample so thatimpingement of the patterned beamlets moves along a first path on thefilm sample between the first edge and the second edge with thepatterned beamlets, and (d) continuously scanning, at a second constantpredetermined speed, the film sample so that impingement of thepatterned beamlets moves along a second path on the film sample betweenthe first edge and the second edge with the patterned beamlets, whereinat least one of the patterned beamlets has a predetermined width and apredetermined length, the predetermined length being greater than thepredetermined width and extending along at least one of the first pathand the second path.
 2. The system of claim 1, wherein, during theexecution of step (c), the processing arrangement continuouslytranslates the film sample so that impingement of the patterned beamletsmoves along the first path, wherein the patterned beamlets irradiatesuccessive first portions of the film sample, the first portions beingmelted while being irradiated and wherein, during the execution of step(d), the processing arrangement continuously translates the film sampleso that impingement of the patterned beamlets moves along the secondpath, wherein the patterned beamlets irradiate successive secondportions of the film sample, the second portions being melted whilebeing irradiated.
 3. The system of claim 2, wherein, after theprocessing arrangement causes the translation of the film sample so thatthe patterned beamlets irradiate a next first successive portion alongthe first path of the film sample, the previously irradiated firstportion along the first path is resolidified, and wherein, after theprocessing arrangement causes the translation of the film sample so thatthe patterned beamlets irradiate a next successive second portion alongthe second path of the film sample, the previously irradiated secondportion along the second path is resolidified.
 4. The system of claim 2,wherein the processing arrangement executes the following additionalsteps: (e) before step (d), positioning the film sample so that thepatterned beamlets impinge on a first location outside of boundaries ofthe film sample with respect to the film sample, and (f) after step (e)and before step (d), microtranslating the film sample so thatimpingement of the patterned beamlets moves from the first location to asecond location, and wherein the processing arrangement executes step(d) with the patterned beamlets initially impinging on the secondlocation.
 5. The system of claim 4, wherein the processing arrangementexecutes the following additional steps: (g) after step (d), translatingthe film sample so that impingement of the patterned beamlets moves to athird location which is outside the boundaries of the film sample, (h)after step (g), stepping the film sample so that impingement of thepatterned beamlets moves from the third location to a fourth location,the fourth location being outside of the boundaries of the film sample,and (i) after step (h), maintaining the film sample so that thepatterned beamlets impinge on the fourth location until any vibration ofthe film sample is damped out.
 6. The system of claim 5, wherein theprocessing arrangement executes the following additional step: (j) afterstep (i), repeating steps (c) and (d) for impingement of the patternedbeamlets along respective third and fourth paths on the film sample. 7.The system of claim 2, wherein, while executing step (c), the processingarrangement continuously translates the film sample in a firstdirection, wherein, while executing step (d), the processing arrangementcontinuously translates the film sample in a second direction, andwherein the processing arrangement executes the following additionalsteps: (k) after step (c), continuously translating at the firstconstant predetermined speed the film sample so that impingement of thepatterned beamlets moves along the first path to reach a first location,wherein the patterned beamlets sequentially irradiate the firstsuccessive portions of the film sample, the film sample being translatedin a direction which is opposite to the first direction, (l) after step(k) and before step (d), microtranslating the film sample so thatimpingement of the patterned beamlets moves from the first location to asecond location, the second location being provided outside ofboundaries of the film sample, and (m) after steps (l) and (d),continuously translating at the second constant predetermined speed thefilm sample so that impingement of the patterned beamlets moves alongthe second path to reach the second location so that the patternedbeamlets sequentially irradiate the second successive portions of thefilm sample, the film sample being translated in a direction which isopposite to the second direction.
 8. The system of claim 7, wherein theprocessing arrangement executes the following additional steps: (n)after step (m), stepping the film sample so that impingement of thepatterned beamlets moves from outside the boundaries of the film samplefrom the second location to a third location, and (o) maintaining thefilm sample so that the patterned beamlets impinge on the third locationuntil any vibrating of the film sample is damped out.
 9. The system ofclaim 8, wherein the processing arrangement executes the followingadditional step: (p) after step (p), repeating steps (c), (d), (k), (l)and (m) for moving the impingement of the patterned beamlets alongrespective third and fourth paths on the film sample.
 10. The system ofclaim 1, wherein the first path is parallel to the second path, wherein,while executing step (c), the processing arrangement causes the filmsample to be continuously scanned in a first direction, and wherein,while executing step (d), the processing arrangement causes the filmsample to be continuously scanned in a second direction, the firstdirection being opposite to the second direction.
 11. The system ofclaim 1, wherein the first edge is located on a side of the film samplewhich is opposite from a side of the film sample at which the secondedge is located.
 12. The system of claim 1, wherein the processingarrangement executes step (c) without stopping when the film sample isimpinged by the patterned beamlets along the first path.
 13. The systemof claim 1, wherein the processing arrangement executes step (d) withoutstopping when the film sample is impinged by the patterned beamletsalong the second path.
 14. A system for processing a silicon thin filmsample to produce a crystalline silicon thin film, the film samplehaving a first edge and a second edge, the system comprising: a storagearrangement storing a computer program; and a processing arrangementwhich, when executing the computer program, is configured to perform thefollowing steps: (a) controlling a laser beam generator to emit a laserbeam, (b) masking portions of the laser beam to generate patternedbeamlets, each of the patterned beamlets impinging on the film sampleand having an intensity which is sufficient to melt the film sample, and(c) continuously scanning, at a constant predetermined speed, the filmsample so that impingement of the patterned beamlets moves along apredetermined path on the film sample between the first edge and thesecond edge with the patterned beamlets, wherein the continuous scanningstep is performed without stopping when the film sample is impinged bythe patterned beamlets along the predetermined path, wherein at leastone of the patterned beam lets has a predetermined width and apredetermined length, the predetermined length being greater than thepredetermined width and extending along at least one of the first pathand the second path.
 15. A system for processing a silicon thin filmsample to produce a crystalline silicon thin film, the film samplehaving a first edge and a second edge, the system comprising: a storagearrangement storing a computer program; and a processing arrangementwhich, when executing the computer program, is configured to perform thefollowing steps: (a) controlling a laser beam generator to emit a laserbeam, (b) masking portions of the laser beam to generate patternedbeamlets, each of the patterned beamlets impinging on the film sampleand having an intensity which is sufficient to melt the film sample, (c)continuously scanning, at a first constant predetermined speed, the filmsample so that impingement of the patterned beamlets moves along a firstpath on the film sample between the first edge and the second edge withthe patterned beamlets, and (d) continuously scanning, at a secondconstant predetermined speed, the film sample so that impingement of thepatterned beamlets moves along a second path on the film sample betweenthe first edge and the second edge with the patterned beamlets, whereinat least one of the first path and the second path extends in adirection which is approximately perpendicular to the direction of graingrowth that occurs upon a re-solidification of particularpreviously-melted portions of the film sample.
 16. A system forprocessing a silicon thin film sample to produce a crystalline siliconthin film, the film sample having a first edge and a second edge, thesystem comprising: a storage arrangement storing a computer program; anda processing arrangement which, when executing the computer program, isconfigured to perform the following steps: (a) controlling a laser beamgenerator to emit a pulsed laser beam, (b) masking portions of thepulsed laser beam to generate patterned beamlets, each of the patternedbeamlets impinging on the film sample and having an intensity which issufficient to melt the film sample, (c) continuously scanning, withoutmicrotranslating and at a first constant predetermined speed, the filmsample so that impingement of the patterned beamlets moves along a firstpath on the film sample between the first edge and the second edge withthe patterned beamlets, and (d) continuously scanning, withoutmicrotranslating and at a second constant predetermined speed, the filmsample so that impingement of the patterned beamlets moves along asecond path on the film sample between the first edge and the secondedge with the patterned beamlets.
 17. The system according to claim 16,wherein the first path extends in a direction which is approximatelyperpendicular to the direction of grain growth that occurs upon are-solidification of particular previously-melted portions of the filmsample.
 18. A system for processing a silicon thin film sample toproduce a crystalline silicon thin film, the film sample having a firstedge and a second edge, the system comprising: a storage arrangementstoring a computer program; and a processing arrangement which, whenexecuting the computer program, is configured to perform the followingsteps: (a) controlling a laser beam generator to emit a laser beam, (b)masking portions of the laser beam to generate patterned beamlets, eachof the patterned beamlets impinging on the film sample and having anintensity which is sufficient to melt the film sample, and (c)continuously scanning, without microtranslating and at a constantpredetermined speed, the film sample so that impingement of thepatterned beamlets moves along a predetermined path on the film samplebetween the first edge and the second edge with the patterned beamlets,wherein the continuous scanning step is performed without stopping whenthe film sample is impinged by the patterned beamlets along thepredetermined path.
 19. The system according to claim 18, wherein thefirst path extends in a direction which is approximately perpendicularto the direction of grain growth that occurs upon a re-solidification ofparticular previously-melted portions of the film sample.
 20. A systemfor processing a silicon thin film sample to produce a crystallinesilicon thin film, the film sample having at least one region whichincludes a first boundary and a second boundary, the system comprising:a storage arrangement storing a computer program; and a processingarrangement which, when executing the computer program, is configured toperform the following steps: (a) controlling a laser beam generator toemit a pulsed laser beam, (b) masking portions of the pulsed laser beamto generate patterned beamlets, each of the patterned beamlets impingingon the at least one region and having an intensity which is sufficientto melt the at least one region, (c) continuously scanning, withoutmicrotranslating and at a first constant predetermined speed, the atleast one region so that impingement of the patterned beamlets movesalong a first path on the at least one region between the first boundaryand the second boundary with the patterned beamlets, and (d)continuously scanning, without microtranslating and at a second constantpredetermined speed, the at least one region so that impingement of thepatterned beamlets moves along a second path on the at least one regionbetween the first boundary and the second boundary with the patternedbeamlets.
 21. The system according to claim 20, wherein the first pathextends in a direction which is approximately perpendicular to thedirection of grain growth that occurs upon a re-solidification ofparticular previously-melted portions of the film sample.
 22. A systemfor processing a silicon thin film sample to produce a crystallinesilicon thin film, the film sample having at least one region whichincludes a first boundary and a second boundary, the system comprising:a storage arrangement storing a computer program; and a processingarrangement which, when executing the computer program, is configured toperform the following steps: (a) controlling a laser beam generator toemit a pulsed laser beam, (b) masking portions of the pulsed laser beamto generate patterned beamlets, each of the patterned beamlets impingingon the at least one region and having an intensity which is sufficientto melt the at least one region, and (c) continuously scanning, withoutmicrotranslating and at a constant predetermined speed, the at least oneregion so that impingement of the patterned beamlets moves along apredetermined path on the at least one region between the first boundaryand the second boundary with the patterned beamlets, wherein thecontinuous scanning step is performed without stopping when the at leastone boundary is impinged by the patterned beamlets along thepredetermined path.
 23. The system according to claim 22, wherein thefirst path extends in a direction which is approximately perpendicularto the direction of grain growth that occurs upon a re-solidification ofparticular previously-melted portions of the film sample.